How to cast from Interface to Actor?

Development Programming & Scripting UI
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1

I have a series of methods that take in a pointer of a type of interface so that any data type that is using the interface can be passed as a parameter and have its interface methods called. I have debug statements that use GetDisplayName() to print the object context with the debug info by its parameter doesn’t accept interface types. How do I type cast from my interface to the correct Actor or UObject type it wants?

void UBuffComponent::PrintAllTankBuffs(TScriptInterface<IBuffableInterface> tankRef, float _debugTime){
	//* This function is for debugging purposes.

	//* Error checking for null pointers.
	if(tankRef == nullptr){
		GEngine->AddOnScreenDebugMessage(-1, _debugTime, FColor::Red, FString(TEXT("(BuffComponent::PrintAllTankBuffs) tankRef is not a valid type.")));
		return;
	}

	FString msg;

	if(tankRef->GetActiveBuffs().Num() == 0){
		msg = FString(TEXT("Active buff list for ")) += UKismetSystemLibrary::GetDisplayName((AActor)tankRef) += FString(TEXT(" Contains no items."));
		GEngine->AddOnScreenDebugMessage(-1, _debugTime, FColor::Magenta, msg);
		return;
	}

	msg = FString(TEXT("Active buff list for ")) += UKismetSystemLibrary::GetDisplayName((AActor)tankRef) += FString(TEXT(" contains ")) += FString::FromInt(tankRef->GetActiveBuffs().Num()) += FString(TEXT(" items."));
	GEngine->AddOnScreenDebugMessage(-1, _debugTime, FColor::Yellow, msg);

	//* Get every buff and print to screen.
	for(int i = 0; i < tankRef->GetActiveBuffs().Num(); i++){
		msg = FString::FromInt(i) += FString(TEXT(" : ")) += UKismetSystemLibrary::GetDisplayName(tankRef->GetActiveBuffs()[i]);
		GEngine->AddOnScreenDebugMessage(-1, _debugTime, FColor::Cyan, msg);
	}
}

error C2440: 'type cast': cannot convert from 'TScriptInterface' to 'AActor'

2

Cast>AActor>(tankRef) and InterfaceCast>AActor>(tankRef) didn’t work. Not sure what I’m missing here.

EDIT:
(Why does > disappear in these forms? I’m not typing html. pls. >.>)

3

I’m not sure what this error means.

CompilerResultsLog:Error: Error S:\DysanianDawnWorkspace\PastryPanzerPanic\Source\PastryPanzerPanic\Private\Buffs\BuffComponent.cpp(43) : error C2665: 'Cast': none of the 2 overloads could convert all the argument types
CompilerResultsLog:Error: Error D:\UnrealEngine\Epic Games\4.14\Engine\Source\Runtime\CoreUObject\Public\UObject\Linker.h(512) : note: could be 'T *Cast<AActor>(FLinker *)'
CompilerResultsLog: Info         with
CompilerResultsLog: Info         [
CompilerResultsLog: Info             T=AActor
CompilerResultsLog: Info         ]
CompilerResultsLog:Error: Error D:\UnrealEngine\Epic Games\4.14\Engine\Source\Runtime\CoreUObject\Public\Templates\Casts.h(270) : note: or       'T *Cast<AActor>(const FSubobjectPtr &)'
CompilerResultsLog: Info         with
CompilerResultsLog: Info         [
CompilerResultsLog: Info             T=AActor
CompilerResultsLog: Info         ]
CompilerResultsLog:Error: Error S:\DysanianDawnWorkspace\PastryPanzerPanic\Source\PastryPanzerPanic\Private\Buffs\BuffComponent.cpp(43) : note: while trying to match the argument list '(TScriptInterface<IBuffableInterface>)'
4

If you are using TScriptInterface, you need to call “GetObject” when doing your cast to an Actor or some other UObject based class:

AActor* MyActor = Cast<AActor>(tankref.GetObject());
FString DisplayName = UKismetSystemLibrary::GetDisplayName(MyActor);

You can see an example of this in the GameplayAbilities blueprint library method "ForwardGameplayCueToTarget".
5

Thanks! I was searching all night trying to figure that out. The doc for TScriptInterface says nothing about GetObject().

6

For what its worth, I know this is old but GetObject is a member of TScriptInterface’s parent class: FScriptInterface | Unreal Engine Documentation